Membrane piston pump or piston pump, respectively

ABSTRACT

Membrane piston pump or piston pump, respectively, with a piston guided in a cylinder which acts upon a chamber to which a pump membrane is assigned, which is on its part facing a pump chamber which is connected to an aspirating connection and a pressure connection via valves, a drive equipment for the piston which is connected to the piston via a piston rod, characterised in that the drive equipment has an electric motor, which is in rotating connection with the cage of a planetary roller thread drive, the threaded spindle of which is axially coupled to the piston rod, the cage being rotatably but axially fixedly beared in a housing of the drive equipment and a path transmitter is provided which creates a path signal in accordance with the path travelled by the threaded spindle, which signal is given up to a control equipment for the electric motor for reversing the rotational direction of the electric motor after a predetermined path of the threaded spindle.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not applicable.

BACKGROUND OF THE INVENTION

he present invention is related to a membrane piston pump or piston pump, respectively, according to the preamble of patent claim 1.

In the first place, membrane piston pumps are used for conveying fluids containing solids. At least one membrane is assigned to a pump chamber, which is enlarged or reduced in its volume according to the rhythm of the membrane movement. The medium is aspirated via an aspirating valve and is delivered via a delivery valve.

It is known to actuate a membrane immediately by a linear drive, a hydraulic cylinder, for instance. Frequently, a hydraulic medium is provided for shifting the membrane in membrane pumps, which is changed in its volume with the aid of a piston. The piston, on its part, can be linearly moved to and from by a drive.

It is known to actuate the piston hydraulically, via a hydraulic pump and a corresponding valve switching arrangement. Further, it is known to provide a rotational motor and to actuate the hydraulic piston by a connecting rod or the like. Both drive methods are disadvantageous in view of the adjustability of the stroke length and also in view of other parameters of the pump operation.

The invention is based on the objective to provide a membrane piston pump or piston pump, respectively, which uses a simply constructed linear drive, by which the stroke length, in particular, can be adjusted in a simple manner.

In the pump according to the invention, the drive equipment has an electric motor, which is in rotational connection with the cage of a planetary roller thread drive, the threaded spindle of which is axially coupled to the piston rod. The cage of the planetary roller thread drive is rotatably beared in the housing of the drive equipment, but is axially fixed.

A planetary roller thread drive of the indicated type is per se known. It is used as a linear adjustment cylinder and is suited for the transmission of large forces at long endurance.

In the invention, a path transmitter is further provided, which generates a path signal in accordance with the path travelled by the threaded spindle, which signal is given up to a control equipment for the electric motor for reversing the rotational direction of the electric motor after a predetermined path of the threaded spindle. The path transmitter is preferably a rotation transmitter, which converts the number of rotations of the treaded spindle into a shifting path of the threaded spindle.

With the aid of such a drive equipment, the stroke length can be variably adjusted in a simple manner by changing the number of rotations. The number of strokes can be changed also, by changing the rotation speed of the electric motor. For this purpose, the electric motor may have a suitable speed control.

A further advantage of the drive equipment according to the invention is that the speed of the hydraulic piston or its acceleration, respectively, can be made variable also. The acceleration has to be geared to the material parameters of the pump on the one hand, but also to the product that is to be pumped, in order to avoid big shocks and excessive strains of the membrane.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows a schematic cross section through a part of a membrane piston pump according to the invention.

FIG. 2 schematically shows the drive equipment for the membrane piston pump according to FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

While this invention may be embodied in many different forms, there are described in detail herein a specific preferred embodiment of the invention. This description is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiment illustrated

In FIG. 1, a membrane 10 of a membrane piston pump can be recognised, which is assigned to a not shown pump space. The pumps space is connected to an aspirating connection and a pressure connection via an aspiration valve and a pressure valve. In FIG. 1, the membrane 10 sits closely on a membrane seat in a retracted position. Through this, the pump space has its maximum volume. On the other side of the membrane 10, a hydraulic chamber 12 is disposed, which is filled with a hydraulic medium. A cylinder liner 14, which accommodates a piston 16, projects into the chamber 12. Upon movement of the piston 16 in the liner 14, the hydraulic medium in the chamber 12 is pressurised in one stroke direction, through which the membrane is shifted to the left from the position shown in FIG. 1, and by doing so it reduces the volume in the pump space. A part of the hydraulic medium is pumped into a space 18 or is pulled out from it, as is commonly known with membrane piston pumps. It will not be gone into this further.

A piston rod 20 is connected to a drive rod 22 of a linear drive 24. The linear drive 24 is represented in more detail in FIG. 2.

The rod 22 is a part of a threaded spindle 26, which runs inside a cage 28. The cage 28 with two axially spaced ring discs 30, 32 has three roller axles, disposed at 120° distance, which extend in parallel to the axle of the threaded spindle 26 and which bear rollers 34, which engage with the convolutions of the threaded spindle 26. The cage 28 is rotatable in a housing 36. Thus, the cage 28 is rotatably beared, but axially fixed. It is driven by an electric motor 38. When driven in one rotational direction, the threaded spindle 26 is moved in one axle direction. When the rotational direction of the motor 38 is reverted, the threaded spindle 26 is moved in the opposite direction. This is indicated by the double arrow 40.

The rotation of the cage 28 is sensed by a rotation transmitter 42, which converts the number of rotations into a path of the threaded spindle 26 and gives up a corresponding signal to a control equipment 44 for the electric motor 38. Thus, the stroke path of the threaded spindle 26 is determined by the number of rotations which is predetermined in the control equipment 44. It is to be understood that this stroke length can be changed (in certain limits, however), and through this the stroke of the membrane 10 can be changed also. By setting the rotation speed of the electric motor 38, the stroke number can be varied. By a corresponding measure in the control device 44, the acceleration after reversing the stroke direction can be adjusted variably also.

The above disclosure is intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the claims where the term “comprising” means “including, but not limited to”. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims.

Further, the particular features presented in the dependent claims can be combined with each other in other manners within the scope of the invention such that the invention should be recognized as also specifically directed to other embodiments having any other possible combination of the features of the dependent claims. For instance, for purposes of claim publication, any dependent claim which follows should be taken as alternatively written in a multiple dependent form from all prior claims which possess all antecedents referenced in such dependent claim if such multiple dependent format is an accepted format within the jurisdiction (e.g. each claim depending directly from claim 1 should be alternatively taken as depending from all previous claims). In jurisdictions where multiple dependent claim formats are restricted, the following dependent claims should each be also taken as alternatively written in each singly dependent claim format which creates a dependency from a prior antecedent-possessing claim other than the specific claim listed in such dependent claim below.

This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto. 

1. Membrane piston pump or piston pump, respectively, with a piston guided in a cylinder which acts upon a chamber to which a pump membrane is assigned, which is on its part facing a pump chamber which is connected to an aspirating connection and a pressure connection via valves, a drive equipment for the piston which is connected to the piston via a piston rod, characterised in that the drive equipment (24) has an electric motor (38), which is in rotational connection with the cage (28) of a planetary roller thread drive, the threaded spindle (26) of which is axially coupled to the piston rod (20), the cage (28) being rotatably but axially fixedly beared in a housing (36) of the drive equipment (24) and a path transmitter (42) is provided which generates a path signal in accordance with the path travelled by the threaded spindle (26), which signal is given up to a control equipment (44) for the electric motor (38) for reversing the rotational direction of the electric motor (38) after a predetermined path of the threaded spindle (26).
 2. Pump according to claim 1, characterised in that the path transmitter (42) has a rotation transmitter which converts the number of rotations of the treaded spindle (26) into a shifting path. 